Clarifier

Abstract: A clarifier for separating suspended solids from waste water to provide clarified water, comprising a generally rectangular tank for containing waste water to be separated, the tank including generally parallel spaced apart first and second sidewalls, each sidewall having upper and lower sidewall portions, and the tank also including upper and lower regions; a first influent passage extending along at least a portion of the first sidewall and comprising an aperture for introducing waste water into the tank; a first effluent passage proximate the influent passage and including a weir over which clarified water flows for removing clarified water from the upper region of the tank. The clarifier preferably includes a baffle mounted to define a space between the first sidewall and the baffle, and a distribution baffle proximate the aperture.

Description: BACKGROUND OF THE INVENTION Field of the Invention The invention relates to liquid treatment apparatus, and more particularly to clarifiers for use in the separation of solids suspended in water or waste water to provide clarified water. Reference to Prior Art Clarifiers are used in water and waste water treatment processes for the separation of suspended solids in the water or waste water to provide clarified effluent. As used herein, "waste water" includes water, waste water, and any other liquid to be treated. Waste water typically enters the tank of such a clarifier through an influent trough. In the tank, heavy waste solids settle to the bottom and form a sludge layer, which is removed from the tank by collectors. Light waste materials rise to the surface and are skimmed off. Clarified water flows over a weir into an effluent trough and is discharged. Clarifiers are commonly either circular or rectangular in shape. An advantage of rectangular clarifiers over circular clarifiers is that arrangements of a plurality of rectangular clarifiers generally require less land area for constructing a given treatment facility than circular clarifiers because rectangular clarifiers can be arranged in closer proximity than circular clarifiers. For example, a plurality of rectangular clarifiers can be arranged side by side in a row. Rectangular clarifiers arranged side by side can share common walls and other common components. Therefore, it is often desirable to utilize rectangular clarifiers due to space and cost considerations. The prior art rectangular claarifiers commonly include an influent trough on one sidewall and an effluent trough located on an opposite sidewall, so that water flows into the tank from the influent trough on one side, across the tank, and out of the tank through the effluent trough on the opposite side. Some prior art circular clarifiers have demonstrated advantage over prior art rectangular clarifiers by providing more efficient separation than the rectangular clarifiers of a similar surface area. This advantage is primarily attributable to different hydraulic characteristics between those prior art circular clarifiers and prior art rectangular clarifiers. A principal cause of their different hydraulic characteristics is that those circular clarifiers and prior art rectangular clarifiers utilize different influent and effluent trough arrangements. Some circular clarifiers have included trough systems wherein the influent and effluent troughs are proximate each other along the periphery of the clarifier. Such a trough system is described in U.S. Patent No. 3,717,257 issued to Boyle on February 20, 1973. A further system is described in U.S. Patent No. 3,395,800 issued to Kraus on August 6, 1968. This document describes a clarifier comprising a circular tank having an elongate influent passage around the periphery thereof which include inlet apertures connected to downcomers. An effluent passage having a weir is also provided around the periphery of the tank, interior to the influent passage. Clarified water flows from the upper portion of the tank over the weir into the effluent passage. In such circular clarifiers, water flows into the tank from the peripheral influent trough toward the center of the circular tank, and then flows toward the center and then back to the effluent trough. SUMMARY OF THE INVENTION The invention provides a rectangular clarifier having improved hydraulic characteristics and separation efficiency. Other features and advantages of the invention are described in the following drawings, description of a preferred embodiment and the claims. According to the present invention there is provided a clarifier for separating suspended solids from waste water to provide clarified water, the clarifier comprising a tank having a wall for containing waste water to he clarified, an elongate influent passage including apertures spaced apart along its length for introducing waste water to the tank, and an effluent passage including a weir having a weir upper edge over which clarified water flows from an upper portion of the tank into the effluent passage, characterised by the tank being rectangular and the tank wall being defined by a pair of opposed first side walls and a pair of opposed second side walls, and the influent and effluent passages being defined by troughs extending in generally parallel side-by-side relation adjacent or spaced from upper portions of the tank wall, wherein the influent and effluent passages extend only in a direction parallel to the first side walls and extend along a length which is a substantial portion of the length of at least one of the side walls. A skirt baffle can be mounted in the tank to define a space between the sidewall and the skirt baffle, and the apertures of the influent passage admit the waste water into the space. Preferably, the clarifier further includes a second influent passage extending along the opposite sidewall, and a second effluent passage proximate the second influent passage. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top view of a clarifier embodying the invention. Figure 2 is a cross sectional view taken along line 2-2 in Figure 1. Figure 3 is a top view similar to Figure 1 and of a second embodiment of the invention. Figure 4 is a cross sectional view taken along line 4-4 in Figure 3. Figure 5 is an enlarged cross sectional view of the area indicated by circle 5 in Figure 2. Figure 6 is a top view of a plurality of clarifiers having a construction as shown in Figure 1 and arranged side by side in a row. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Illustrated in Figure 1 is a preferred embodiment of a clarifier 1 of the invention for separating suspended solids from waste water to provide clarified effluent. The clarifier 1 includes a generally rectangular tank 2, a first influent passage 3, and a first effluent passage 4. First influent passage 3 is in open communication with tank 2 for introducing waste water containing suspended solids thereto. First effluent passage 4 is in open communication with tank 2 for removing clarified effluent therefrom. The illustrated embodiment of the invention includes a primary waste water feed inlet 5 in open communication with first influent passage 3 for providing waste water thereto. In other arrangements of the invention other structures could be used for providing waste water to first influent passage 3. The illustrated embodiment of the invention also includes primary clarified effluent outlet 6 in open communication with first effluent passage 4 for removing clarified effluent therefrom. In other arrangements of the invention other structures could be used for removing clarified water from first effluent passage 4. As shown in Figure 2, tank 2 for containing waste water to be clarified includes a bottom 9. Returning to Figure 1, tank 2 also includes spaced apart endwalls 10 and spaced apart generally parallel first and second sidewalls 11,12. As shown in Figure 2, the first and second sidewalls 11,12 each include an upper sidewall portion 13 and a lower sidewall portion 14. The tank 2 also includes an upper liquid region 15 and a lower liquid region 16. Returning to Figure 1, first influent passage 3 includes a plurality of apertures 17 in the bottom wall of the trough forming influent passage 3, the apertures 17 providing for flow from the influent passage 3 down into the tank 2. In the embodiment of the invention illustrated in Figure 5, clarifier 1 includes a plurality of distribution baffles 18, one proximate and beneath each aperture 17. In other arrangements of the invention other structures could be used to provide for distribution of flow from the apertures 17. Each distribution baffle 18 is supported by rods 19. In the embodiment of the invention shown in Figure 5, the first effluent passage 4 includes a weir 20 having a weir upper edge 20a, over which clarified water flows from upper region 15. In other arrangements of the invention other structures could be used to provide for flow of clarified water into first effluent passage 4. In the embodiment of the invention illustrated in Figure 5, clarifier 1 also includes a baffle 21 mounted in the tank 2 proximate but in spaced relation from first sidewall 11, to define a space 22 into which waste water is introduced as it flows through apertures 17. In the embodiment of the invention illustrated in Figure 2, a deflector surface 23 is provided proximate the lower sidewall portion 14 of first sidewall 11 and sloping downwardly from lower sidewall portion 14 to bottom 9. In other arrangements of the invention other structures could be used to provide for deflection of solids away from first sidewall 11 as the waste water flows into the tank. In the embodiment of the invention shown in Figure 5, the first influent passage 3 is a first trough having an open top, and the first effluent passage 4 is a second trough having an open top. In other arrangements of the invention other constructions of the influent and effluent passages 3 and 4 could be used. First influent passage 3 is a first trough including influent outside wall 24 having influent outside upper edge 24a, influent bottom 25, and influent inside wall 26 having influent inside upper edge 26a. Apertures 17 are located in the influent bottom 25 for introducing waste water into space 22. In the illustrated embodiment, influent outside wall 24 is formed by a portion of the upper sidewall portion 13 of the first sidewall 11, so that first influent passage 3 extends generally parallel to at least a portion of the upper sidewall portion 13 of the first sidewall 11. In other arrangements of the invention other configurations could be used, such that influent passage 3 may be spaced apart from the first sidewall 11, or may only extend along part of the first sidewall 11. The first effluent passage 4 includes effluent outside wall 27 having effluent outside upper edge 27a, effluent bottom 28, and effluent inside wall 29. in the illustrated embodiment of the invention, effluent inside wall 29 includes weir 20 having weir upper edge 20a. In other arrangements of the invention other constructions could be used to provide clarified water to first effluent passage 4. Influent outside upper edge 24a and influent inside upper edge 26a are higher than weir upper edge 20a, so that the level L i of water in first influent passage 3 is higher than the level L c of water in first effluent passage 4 and the level L t of water in the tank 2. In the illustrated embodiment of the invention, effluent outside wall 27 and influent inside wall 26 are formed by a common wall 30, so that the first effluent passage 4 is adjacent to and extends along the first influent passage 3 in generally parallel side by side relation. Other arrangements of the invention could use other constructions of the first influent passage 3 and first effluent passage 4. For example, they may be spaced apart somewhat or of different lengths. In the illustrated embodiment, a shelf 31 projecting from the upper sidewall portion 13 includes both the first influent passage 3 and first effluent passage 4. In other arrangements of the invention, other structures could be used to support the passages. Returning to Figure 1, the first influent passage 3 includes an influent passage inlet end 32, a closed influent passage terminal end 33 terminating at influent end wall 34, an influent passage width, and an influent passage length. The first effluent passage 4 includes an effluent passage outlet end 35, a closed effluent passage terminal end 36 terminating at effluent end wall 37, an effluent passage width and an effluent passage length. In the illustrated embodiment of the invention the influent passage width progressively decreases from the influent passage inlet end 32 along the influent length to the influent passage terminal end 33, and the effluent passage width progressively increases from the effluent passage terminal end 36 along the effluent passage length to the effluent passage outlet end 35. In the illustrated embodiment, the influent passage inlet end 32 is also proximate the effluent passage terminal end 36, so that the influent passage width and effluent passage width together comprise a uniform total width along the length of the passages. In other arrangements of the invention, other constructions and configurations of the influent passage 3 and effluent passage 4 could be used. While the clarifier could have other constructions for removing sludge, in the specific arrangement shown in Figures 1 and 2, the clarifier includes sludge hoppers 38 (not shown in Figure 2) for receiving separated solids from the bottom 9 of tank 2. A collector conveyor 39 having collector flights 40 scrapes or fluidizes the separated solids from the bottom 9 into the sludge hoppers 38. The illustrated clarifier 1 also includes a scum pipe 41 having scum openings 42 and connected to a scum box (not shown). The scum openings 42 of scum pipe 41 are located at the level L t of water in the tank 2, for receiving floating solids skimmed from the upper region 15 by collector flights 40. The scum box receives skimmed solids from scum pipe 41 for removal from clarifier 1. In other arrangements of the invention other structures could be used to provide for removal of floating solids. In a second embodiment of the invention illustrated in Figures 3 and 4, clarifier 1 includes a second influent passage 7 extending along upper sidewall portion 13 of the second or opposite sidewall 12. A second effluent passage 8 is adjacent to and extends along second influent passage 7 in generally parallel side by side relation. A second skirt baffle 21 is mounted proximate second sidewall 12, to define a second space 22 into which waste water is introduced through apertures 17. A second deflector surface 23 slopes downwardly from second sidewall 12 to bottom 9. As illustrated in Figure 6, in one embodiment of the invention a plurality a clarifiers 1 can be arranged side by side in a row to minimize the land area or footprint required for building a treatment facility. The side by side clarifiers 1 can also utilize common elements, such as common sidewalls 12a-11b, 12b-11c, 12c-11d and 12d-11e, and a common primary waste water feed inlet 5 and primary clarified water outlet 6. While a clarifier of the invention may include both first and second influent and effluent passages 3,4,7 and 8, the operation of a clarifier 1 having only a first influent passage 3 and first effluent passage 4 will be described. In operation, waste water containing suspended solids enters primary waste water inlet 5 and passes into first influent passage 3 at influent inlet end 32. The waste water flows through influent passage 3 and apertures 17 into space 22 of tank 2. The introduced waste water is distributed generally horizontally in space 22 by distribution baffles 18. The waste water flows downwardly through space 22 and under skirt baffle 21, and may deflect off deflector surface 23, into lower region 16. In lower region 16, waste water flows generally horizontally away from first sidewall 11. From lower region 16 the waste water enters upper region 15. In upper region 15, waste water rises vertically upwardly with a horizontal component away from weir 20. Heavy solids settle to the bottom 9, where they are scraped by collector flights 40 of collector conveyor 39 into sludge hoppers 38 and are thereby removed from the tank 2. Light solids reaching the water surface are skimmed by collector flights 40 of collector conveyor 39 through scum openings 42 into scum pipe 41. Skimmed solids pass from scum pipe 41 into the scum box for removal from clarifier 1. After rising to the upper region 15, clarified water flows with a horizontal component towards weir 20 and overflows weir upper edge 20a into first effluent passage 4. The clarified water passes out of first effluent passage 4 at effluent outlet end 35, and into primary clarified water outlet 6 for removal from clarifier 1.

Claims: A clarifier (1) for separating suspended solids from waste water to provide clarified water, the clarifier comprising a tank (2) having a wall for containing waste water to be clarified, an elongate influent passage (3) including apertures (17) spaced apart along its length for introducing waste water to the tank (2), and an effluent passage (4) including a weir (20) having a weir upper edge (20a) over which clarified water flows from an upper portion (15) of the tank (2) into the effluent passage (4), characterised by the tank (2) being rectangular and the tank wall being defined by a pair of opposed first side walls (11,12) and a pair of opposed second side walls (10), and the influent and effluent passages (3,4) being defined by troughs extending in generally parallel side-by-side relation adjacent or spaced from upper portions (13) of the tank wall, wherein the influent and effluent passages (3,4) extend only in a direction parallel to the first side walls (11,12) and extend along a length which is a substantial portion of the length of at least one of the side walls. The clarifier according to claim 1 wherein the influent passage (3) includes an influent outside wall (24) having an influent outside upper edge (24a), an influent bottom (25) and an influent inside wall (26) having an influent inside upper edge (26a), and wherein the effluent passage (4) includes an effluent outside wall (27) having an effluent outside upper edge (27a), an effluent bottom (28, and an effluent inside wall (29) including said weir (20) and said weir upper edge (20a). The clarifier according to claim 2 wherein the weir upper edge (20a) of the effluent passage (4) is lower than the influent outside upper edge (24a) and influent inside upper edge (26a) of the influent trough. The clarifier according to any preceding claim comprising a skirt baffle (21) mounted in the tank (2) to define between a first sidewall (11,12) and the skirt baffle (21) a space in communication with a lower portion (16) of the tank (2), and wherein the aperture (17) of the influent passage (3) are located to admit waste water into the space. The clarifier according to claim 4 comprising distribution baffles (18) mounted in the tank (2) proximate the aperture (17). The clarifier according to any preceding claim wherein the influent passage (3) and the effluent passage (4) each have a width, a length and inlet and outlet ends respectively, and wherein the influent passage width progressively decreases from the influent passage inlet end (32) along the influent passage length to the influent passage outlet end (33), and wherein the effluent passage width progressively increases from the effluent passage inlet end (36) along the effluent passage length to the effluent passage outlet end (35). The clarifier according to claim 6 wherein the influent passage inlet end (32) is proximate the effluent passage inlet end (36), and the influent passage width and effluent passage width together comprise a uniform total width along the lengths of the passages. The clarifier according to any preceding claim, comprising a shelf projecting into the tank (2) from the upper sidewall portion of a first sidewall (11,12), and wherein the shelf comprises the influent passage (3) and the effluent passage (4). The clarifier according to any preceding claim, comprising a primary waste water feed inlet (5) in open communication with the influent passage (3) and a primary clarified water outlet (6) in open communication with the effluent passage (4). The clarifier according to any preceding claim, comprising a second influent passage (7) extending along at least a portion of the upper wall portion (13) of the second (12) of the pair of opposed first sidewalls (11,12) and a second effluent passage (8) proximate the second influent passage (7).

Inventors: BOYLE WILLIAM H, BOYLE, WILLIAM H.
Applicants: UNITED STATES FILTER CORP, UNITED STATES FILTER CORPORATION
Application year: 1994
Main classification: B01D21
IPC codes: B01D21